The disclosures herein relate generally to pressure gauges and more particularly to such gauges used in semi-conductor fabrication process equipment.
A typical Bourdon tube pressure gauge system includes a socket body connected to adapt a Bourdon tube to a process connection. The tube is exposed to a pressurized gas supply measured by a gauge, or a compound gauge which indicates pressure and/or a vacuum present in the Bourdon tube. A cap on a distal end of the tube connects to a mechanical linkage. The tube flexes under pressure and the cap moves to actuate the linkage which drives a pointer indicating an analog reading. The reading is in pounds per square inch of positive pressure or in inches of Mercury (Hg) of vacuum pressure.
In semi-conductor fabrication processes, pressure gauges are used to monitor gas pressure in ultra high purity gas distribution systems. In a typical semi-conductor fabrication process, more than 250 gases are used to manufacture semi-conductor devices. Gas sources include bottles, cylinders, or bulk gas supplies. Before a gas source can be connected to an ultra high purity gas distribution system, the gas system must be purged from impurities and moisture. This purging process is known as dry down. The factors that affect dry down time are internal volume and surface finish of the gas system including piping, fittings, components, etc. Dry down can be very time consuming, often several days.
Also, in semi-conductor fabrication processes, pressure gauges are used to monitor gas pressure in ultra high purity gas distributions systems. However, a typical semi-conductor fabrication process uses a variety of chemically corrosive gases to manufacture semi-conductor devices. When corrosive gases are trapped in crevices, microscopic corrosion occurs generating particulate. Particulate in turn can flow through the gas system into the semi-conductor device which in turn destroys the semi-conductor reducing process yield. Therefore, the goal of an ultra high purity gas distribution system is to include components that are free from crevices, and other surface imperfections that create particle generation sites.
Therefore, what is needed is an apparatus and a method which provides a pressure gauge system with minimal internal volume, an internal surface finish that does not sacrifice functional performance, and a crevice free connection between the tube and the socket body to reduce particulate generation when exposed to chemically corrosive gases used in semi-conductor high purity gas distribution systems.